The Pitting And Repassivation Behavior Of 2205 Duplex Stainless Steel

2205DSS is used as a structural material in corrosion environment, such as desalination of sea water and petrochemical industry. The environment in service for 2205DSS is severe, containing aggressive Cl- ions. The pitting corrosion of 2205DSS will be induced by the presence of Cl" ions due to its small size and high penetrability, threatening the safety and reliability of the DSS in service. Thus, understanding the behavior of pitting corrosion and repassivation of DSS is an urgent issue for their special application.CPT and PRT are used to characterize pitting corrosion and repassivation of passive materials. In the present work, CPT and PRT of 2205DSS were measured by cyclic polarization. The effect of the presence of Cl- ions on CPT and PRT was investigated, and the results indicated that Cl- ions are more affected PRT than CPT. The cyclic polarization exhibits much excellent accuracy and reliability compared with temperature cyclic polarization. The pitting resistance of 2205DSS is superior to that of 316LSS by the analysis of pitting and repassivation behavior.An increase in temperature and Cl- ions concentration corresponded to a decrease in pitting resistance of 2205DSS under various corrosion electrochemical parameters conducted by cyclic polarization and M-S measurement. The structure of passive film on 2205DSS changed with temperature. An incubation period of pitting corrosion was performed by the potentiostatic method. The results suggested that, the pitting susceptibility could increase at the solution temperature less than CPT. However, the pitting corrosion could not happen under the passive potential region below the PRT, and the passive film will be repaired soon after breakdown. A decrease in incubation period contributed to an increase in pitting susceptibility above the CPT. Meanwhile, the pit initial position of 2205DSS was attributed to the inclusion in the substrate. A similar incubation period of pitting corrosion behavior for 316LSS was observed. However, the pitting corrosion could happen at all conditions.